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Lime softening (also known as lime buttering, lime-soda treatment, or Clark's process) [1] is a type of water treatment used for water softening, which uses the addition of limewater (calcium hydroxide) to remove hardness (deposits of calcium and magnesium salts) by precipitation.
Each mole of CO 2 (44 g) reacts with one mole of calcium hydroxide (74 g) and produces one mole of water (18 g). The reaction can be considered as a strong-base-catalysed, water-facilitated reaction. [5] The reaction mechanism of carbon dioxide with soda lime can be decomposed in three elementary steps:
Both quick- and hydrated lime are used in the treatment of drinking water. [10] Petroleum industry: Water detection pastes contain a mix of calcium oxide and phenolphthalein. Should this paste come into contact with water in a fuel storage tank, the CaO reacts with the water to form calcium hydroxide.
Rain water contains dissolved carbon dioxide taken from the atmosphere. Some of the dissolved carbon dioxide reacts with the water to form carbonic acid, which remains in solution. Minerals containing calcium and magnesium form soluble bicarbonates when exposed to carbonic acid. Water containing these minerals is known as "hard water".
Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH) 2 ) in the cement reacts with carbon dioxide (CO 2) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5.
The reduction of blowdown by dealkalization keeps the water treatment chemicals in the boiler longer, thus minimizing the amount of chemicals required for efficient, noncorrosive operation. [2] Carbonate and bicarbonate alkalinities are decomposed by heat in boiler water releasing carbon dioxide into the steam.
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Gas exsolution can also occur when the confining pressure is released such as removing the top off a beer bottle or where subsurface water is flowed into an atmospheric pressure tank. As new cold water with dissolved calcium carbonate/bicarbonate is added and heated, the process continues: CO 2 gas is again removed, carbonate concentration ...